Kinetics of nitrate reductive denitrification by nanoscale zero-valent iron

Nanoscale zero-valent iron (Fe0) was synthesized for nitrate denitrification. The reduction efficiency of nitrate decreased quickly with increasing initial pH value, increased considerably with the increasing dosage of nanoscale Fe0, and did not vary much with initial nitrate concentrations changing from 20 to 50 mg l−1 when the excessive amount of nanoscale Fe0 was utilized. With reductive denitrification of nitrate by nanoscale Fe0, the removal rate of nitrate reached 96.4% in 30 min with nanoscale Fe0 dosage of 1.0 g l−1 and pHin 6.7, and more than 85% of the nitrate was transformed into ammonia. Kinetics analysis in batch studies demonstrates that the denitrification of nitrate by nanoscale Fe0 involves reaction on the metal surface, which fits well the pseudo-first order reaction with respect to nitrate concentration. The observed reaction rate constant of reductive denitrification of nitrate was determined to be 0.086 min−1 with a nanoscale Fe0 dosage of 1.0 g l−1 and pHin 6.7. Fast and highly effective denitrification can be achieved by nanoscale Fe0 compared with commercial Fe0 powder, this is due to the extremely high surface area and high reactivity for nanoscale Fe0, which can enhance the denitrification efficiencies remarkably.

Research highlights▶ The denitrification of nitrate by synthesized nanoscale Fe0 is fast and effective. ▶ The denitrification depend on initial pH value and the dosage of nanoscale Fe0. ▶ The main end product of the denitrification is ammonia instead of nitrogen. ▶ The denitrification by nanoscale Fe0 fits well the pseudo-first order reaction.